1. Field of the Invention
The present invention relates to a circuit arrangement comprising two feed circuits connectible to a load having mutually opposite poling and comprising a pair of leads for a load resistor respectively connected to the feed circuits via feed current paths and comprising means for optionally feeding of the load resistor by way of one or the other feed circuit.
2. Description of the Prior Art
A circuit arrangement of the type generally set forth above is already known from the German published application 32 16 497, fully incorporated herein by this reference. Given this known circuit arrangement, the feed circuit is composed of a constant current source. The further feed circuit is obtained by connecting a voltage limiter to the constant current source. In view of personal protection in the locating position, a reduction of the device voltage to, for example a maximum of 60V is provided.
The two feed circuits are conducted by way of a common pair of feed current paths to a transfer device which optionally connects the load resistor to one or the other polarity and the two feed current paths. A relay which enables a automatic error locating and is correspondingly driven serves as a transfer device.
The load resistor is a remote feed loop which feeds a plurality of series-connected loads with constant direct current. The remote feed loop is provided with shunt arms which respectively contain a diode poled in the reverse direction for the remote feed loop and the resistor disposed in series therewith. When the test voltage poled opposite the remote feed voltage is applied to the input of the remote feed loop and when the remote feed loop is interrupted at any location whatsoever, a current then flows in all shunt arms which lie upstream of the interruption. The sum current is measured at the feed location. An interrupted repeater section is assigned to every measured value.
The remote feed device is switched from constant current to constant voltage. This becomes all the more difficult the higher the remote feed power in relationship to the locating power. Further, inverting the poles becomes relatively complicated given serious operation of remote feed devices.
Another possibility for optionally feeding an electrical load with voltages of different polarity resides in the utilization of mechanical contacts having manual activation.
W. S. Jahn, "Elektrisch fernuberwachen und Fernbedienen", 1962, Richard Pflaum Verlag, Munich, Page 218, also discloses that electrical lines in electrical remote control can be multiply exploited in that remote control signals having different polarity are employed.